Coating medical devices

• US 20030143315A1
• Filed: 11/21/2002
• Published: 07/31/2003
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Da-Ren Chen, David Y.H. Pui
• Original Assignee: Da-Ren Chen, David Y.H. Pui
• Inventors: Chen, Da-Ren, Pui, David Y.H.
• Granted Patent: US 7,247,338 B2
• Time in Patent Office: Days
• US Class Current: 427/2.1
• CPC Class Codes: A61F 2/86 Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
• CPC Class Codes: A61L 2300/00 Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
• CPC Class Codes: A61L 2300/622 Microcapsules
• CPC Class Codes: A61L 2420/02 Methods for coating medical devices
• CPC Class Codes: A61L 31/10 Macromolecular materials
• CPC Class Codes: A61L 31/16 Biologically active materials, e.g. therapeutic substances A61L31/047 takes precedence
• CPC Class Codes: B05B 1/14 with multiple outlet openings B05B1/02, B05B1/26 take precedence; with strainers in or outside the outlet opening
• CPC Class Codes: B05B 13/0228 the movement of the objects being rotative B05B13/0242 takes precedence
• CPC Class Codes: B05B 5/025 Discharge apparatus, e.g. electrostatic spray guns
• CPC Class Codes: B05B 5/0255 spraying and depositing by electrostatic forces only
• CPC Class Codes: B05B 5/03 characterised by the use of gas , e.g. electrostatically assisted pneumatic spraying B05B5/04, B05B5/043, B05B5/047 take precedence
• CPC Class Codes: B05B 5/0533 Electrodes specially adapted therefor; Arrangements of electrodes
• CPC Class Codes: B05B 5/08 Plant for applying liquids or other fluent materials to objects
• CPC Class Codes: B05B 5/082 characterised by means for supporting, holding or conveying the objects
• CPC Class Codes: B05B 7/066 with an inner liquid outlet surrounded by at least one annular gas outlet
• CPC Class Codes: B05B 7/0884 the outlet orifices for jets constituted by a liquid or a mixture containing a liquid being aligned
• CPC Class Codes: B05D 1/002 the substrate being rotated
• CPC Class Codes: B05D 1/04 involving the use of an electrostatic field B05D1/025 and B05D1/14 take precedence
• CPC Class Codes: B05D 1/045 on non-conductive substrates

Abstract

Methods and systems for coating at least a portion of a medical device (e.g., a stent structure) include providing a plurality of coating particles (e.g., monodisperse coating particles) in a defined volume. For example, the particles may be provided using one or more nozzle structures, wherein each nozzle structure includes at least one opening terminating at a dispensing end. The plurality of coating particles may be provided in the defined volume by dispensing a plurality of microdroplets having an electrical charge associated therewith from the dispensing ends of the one or more nozzle structures through use of a nonuniform electrical field between the dispensing ends and the medical device. Electrical charge is concentrated on the particle as the microdroplet evaporates. With a plurality of coating particles provided in the defined volume, such particles can be moved towards at least one surface of the medical device to form a coating thereon (e.g., using an electric field and/or a thermophoretic effect).

Claims

1. A method of coating at least a portion of a medical device, the method comprising:

providing a medical device in a defined volume, wherein the medical device comprises at least one surface;

providing a plurality of monodisperse coating particles in the defined volume, wherein the plurality of monodisperse coating particles have a nominal diameter of less than 10 micrometers and a geometrical standard deviation of less than 1.2; and

moving a plurality of the coating particles towards the at least one surface of the medical device to form a coating thereon.

2. The method of claim 1, wherein providing the plurality of monodisperse coating particles comprises providing an electrical charge on the plurality of monodisperse coating particles, and further wherein moving the plurality of monodisperse coating particles towards the at least one surface of the medical device to form a coating thereon comprises moving the plurality of monodisperse coating particles towards the medical device using an electrical field.

3. The method of claim 2, wherein providing the plurality of monodisperse coating particles comprises dispensing a spray of microdroplets having an electrical charge associated therewith, wherein each of the microdroplets comprises a particle, wherein the electrical charge is concentrated on the particle as the microdroplet evaporates, and further wherein the electrical charge of the microdroplet concentrated on the particle is greater than about 30 percent of the Rayleigh charge limit for the microdroplet.

4. The method of claim 3, wherein the electrical charge of the microdroplet concentrated on the particle is greater than about 50 percent of the Rayleigh charge limit for the microdroplet.

5. The method of claim 2, wherein providing the plurality of monodisperse coating particles comprises dispensing a spray of microdroplets having an electrical charge associated therewith, wherein each of the microdroplets comprises a particle, wherein the electrical charge is concentrated on the particle as the microdroplet evaporates, and further wherein, prior to contact with the at least one surface of the medical device, a residual particle volume occupied by the evaporated microdroplet comprises less than about 20 percent of a solvent component of the microdroplet.

6. The method of claim 2, wherein the method further comprises creating an electrical field between an electrode and the medical device after the monodisperse coating particles are provided in the defined volume.

7. The method of claim 2, wherein providing the plurality of monodisperse coating particles comprises:

providing one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end thereof from which a plurality of monodisperse coating particles having an electrical charge applied thereto is dispensed; and

dispensing the plurality of monodisperse coating particles from each nozzle structure by creating a nonuniform electrical field between the dispensing ends from which the plurality of monodisperse coating particles are dispensed and the medical device.

8. The method of claim 7, wherein moving the plurality of monodisperse coating particles towards the at least one surface of the medical device to form a coating thereon comprises moving the plurality of monodisperse coating particles towards the medical device using the nonuniform electrical field created between the dispensing ends from which the plurality of monodisperse coating particles are dispensed and the medical device.

9. The method of claim 8, wherein the medical device comprises a structure defining an interior volume, wherein the structure comprises at least an interior surface adjacent the interior volume and at least an exterior surface that is not adjacent to the interior volume, wherein providing the one or more nozzle structures comprises providing at least one nozzle structure having at least one opening at the dispensing end thereof located within the interior volume defined by the structure, and further wherein dispensing the plurality of monodisperse coating particles from the at least one nozzle structure comprises creating a nonuniform electrical field between the dispensing end of the at least one nozzle and the medical device.

10. The method of claim 9, wherein the at least one nozzle structure comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

11. The method of claim 7, wherein providing the one or more nozzle structures comprises providing a plurality of nozzle structures, wherein dispensing the plurality of monodisperse coating particles from the plurality of nozzle structures comprises creating a nonuniform electrical field between the dispensing ends thereof and the medical device.

12. The method of claim 7, wherein providing the medical device comprises providing a medical device in a fixed position within the defined volume.

13. The method of claim 7, wherein providing the medical device comprises providing a medical device that is movable within the defined volume.

14. The method of claim 1, wherein providing the medical device comprises providing a stent structure defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent a defined interior volume and at least an exterior surface that is not adjacent to the defined interior volume.

15. The method of claim 14, wherein providing the plurality of monodisperse coating particles comprises:

providing one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end thereof from which a plurality of monodisperse coating particles having an electrical charge applied thereto is dispensed; and

dispensing the plurality of monodisperse coating particles from each nozzle structure by creating a nonuniform electrical field between the dispensing ends from which the plurality of monodisperse coating particles are dispensed and the stent structure device.

16. The method of claim 15, wherein method further comprises adjusting the strength of the nonuniform electrical field to prevent particles from reaching the interior surface of the stent structure.

17. The method of claim 16, wherein providing the one or more nozzle structures comprises providing at least one nozzle structure having at least one opening at the dispensing end thereof located within the interior volume defined by the stent structure, and further wherein dispensing the plurality of monodisperse coating particles from the at least one nozzle structure comprises creating a nonuniform electrical field between the dispensing end thereof and the stent structure.

18. The method of claim 1, wherein moving the plurality of monodisperse coating particles towards the at least one surface of the medical device comprises using a thermophoretic effect to move the plurality of monodisperse coating particles towards the at least one surface of the medical device.

19. The method of claim 18, wherein providing the medical device comprises providing a stent structure defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent an interior volume and an exterior surface, wherein the method further comprises positioning the stent structure such that the stent axis coincides with an axis of an elongated element located within the interior volume of the stent structure, and further wherein moving a plurality of coating particles towards the at least one surface of the stent structure to form a coating thereon comprises holding the elongated element at a lower temperature than the temperature in the defined volume adjacent the exterior surface of the stent structure such that thermophoretic effect moves the coating particles towards the at least one surface of the stent structure.

20. The method of claim 1, wherein providing the medical device comprises providing a cylindrical stent structure defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent an interior volume and at least an exterior surface that is not adjacent to the interior volume, wherein moving a plurality of monodisperse coating particles towards the at least one surface of the stent structure to form a coating thereon comprises at least rotating the stent structure about the stent axis.

21. The method of claim 1, wherein moving a plurality of monodisperse coating particles towards the at least one surface of the medical device to form a coating thereon comprises moving the stent structure linearly along the stent axis.

22. The method of claim 1, wherein the method further comprises controlling the amount of monodisperse coating particles provided into the defined volume.

23. The method of claim 1, wherein the plurality of coating particles have a nominal diameter of greater than about 1 nanometer and less than about 100 nanometers.

24. The method of claim 1, wherein the plurality of coating particles comprise at least one biologically active ingredient or a coated biologically active ingredient.

25. The method of claim 24, wherein the plurality of coating particles comprise at least one of DNA or coated DNA.

26. A method of coating at least a portion of a medical device, the method comprising:

providing a medical device in a defined volume, wherein the medical device comprises at least one surface;

providing one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end;

providing a plurality of coating particles in the defined volume, wherein providing the plurality of coating particles comprises dispensing a plurality of microdroplets having an electrical charge associated therewith from the dispensing ends of the one or more nozzle structures by creating a nonuniform electrical field between the dispensing ends and the medical device, wherein each of the microdroplets comprises at least a particle, and further wherein the electrical charge is concentrated on the particle as the microdroplet evaporates; and

moving the plurality of coating particles towards the medical device to form a coating on the at least one surface of the medical device using the nonuniform electrical field created between the dispensing ends from which the plurality of coating particles is established and the medical device.

27. The method of claim 26, wherein the plurality of coating particles in the defined volume have a nominal diameter of less than 10 micrometers and a geometrical standard deviation of less than 1.2.

28. The method of claim 26, wherein providing the plurality of microdroplets comprises providing a plurality of microdroplets having electrical charge associated therewith that is greater than about 30 percent of the Rayleigh charge limit for the microdroplet.

29. The method of claim 26, wherein prior to contact with the at least one surface of the medical device, a residual particle volume occupied by the evaporated microdroplet comprises less than about 20 percent of a solvent component of the microdroplet.

30. The method of claim 26, wherein providing the medical device comprises providing a stent structure defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent a defined interior volume and at least an exterior surface.

31. The method of claim 30, wherein the method further comprises adjusting the strength of the nonuniform electrical field to prevent particles from reaching the interior surface of the stent structure.

32. The method of claim 30, wherein providing the one or more nozzle structures comprises providing at least one nozzle structure having at least one opening at the dispensing end thereof located within the defined interior volume of the stent structure, and further wherein dispensing the plurality of monodisperse coating particles from the at least one nozzle structure comprises creating a nonuniform electrical field between the dispensing end thereof and the stent structure.

33. The method of claim 32, wherein the at least one nozzle structure comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

34. The method of claim 30, wherein moving the plurality of coating particles towards the at least one surface of the stent structure to form a coating thereon comprises at least rotating the stent structure about the stent axis relative to the one or more nozzle structures.

35. The method of claim 30, wherein moving the plurality of coating particles towards the at least one surface of the medical device to form a coating thereon comprises moving the stent structure linearly along the stent axis relative to the one or more nozzle structures.

36. The method of claim 30, wherein the method further comprises controlling the amount of coating particles provided into the defined volume.

37. The method of claim 30, wherein the plurality of coating particles have a nominal diameter of greater than about 1 nanometer and less than about 100 nanometers.

38. The method of claim 30, wherein the plurality of coating particles comprises at least one biologically active ingredient or at least one coated biologically active ingredient.

39. The method of claim 30, wherein providing the stent structure comprises providing a medical device in a fixed position within the defined volume during coating of the stent structure.

40. The method of claim 30, wherein each of the nozzle structures comprises at least a first and second opening terminating at the dispensing end of each nozzle structure.

41. The method of claim 30, wherein the method further comprises:

providing an elongated cylindrical body member defining an interior volume thereof along an axis;

positioning the stent structure along the axis of the elongated cylindrical body member; and

positioning a plurality of nozzle structures radially about the axis of the elongated cylindrical body member and linearly along the elongated cylindrical body member in the direction of the axis thereof.

42. The method of claim 41, wherein each of a plurality of the nozzle structures comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

43. The method of claim 41, wherein each of a plurality of the nozzle structures comprises a tapered portion used to define an opening, and further wherein at least a part of each of the plurality of the nozzle structures extend from an integral conductive portion associated with the body member.

44. The method of claim 41, wherein each of a plurality of the nozzle structures comprises a solid post along a center axis extending through an opening at the dispensing end.

45. The method of claim 41, wherein each of a plurality of the nozzle structures comprises an elongated radial opening in the body member.

46. The method of claim 41, wherein each of a plurality of the nozzle structures comprises an elongated opening in the body member lying parallel to the axis thereof.

47. The method of claim 30, wherein the method further comprises:

positioning the stent structure such that the stent axis coincides with an axis of an elongated element; and

using spacing elements to maintain a distance between the stent structure and the elongated element.

48. The method of claim 30, wherein the method further comprises:

positioning the stent structure such that the stent axis coincides with an axis of an elongated element, wherein the elongated element is sized based on the defined interior volume of the stent structure such that a surface of the elongated element is in direct contact with the interior surface of the stent structure; and

removing the elongated element from the interior volume of the stent structure after a plurality of coating particles are moved towards the exterior surface of the stent structure to form a coating thereon.

49. The method of claim 48, wherein the stent structure comprises open framework comprising stent material lying radially from the stent axis and a configuration of openings separating portions of the stent material, wherein the elongated element is sized to stretch the stent structure from a normal state.

50. The method of claim 48, wherein the stent structure comprises open framework comprising stent material lying radially from the stent axis and a configuration of openings separating portions of the stent material, and further wherein the elongated element is removed from the interior volume of the stent structure after a plurality of coating particles are moved towards the exterior surface of the stent structure resulting in a sheath over the open framework including the openings separating portions of the stent material.

51. The method of claim 30, wherein the stent structure comprises open framework comprising stent material lying radially from the stent axis and a configuration of openings separating portions of the stent material, wherein the method further comprises:

providing a conductive elongated element along the axis of the stent structure, wherein the stent structure and the conductive elongated element are spaced a distance apart; and

creating an electric field between the conductive elongated element and the stent structure that is opposite the nonuniform electric field created between the dispensing ends of the nozzle structures and the stent structure.

52. The method of claim 30, wherein the stent structure comprises open framework comprising stent material lying radially from the stent axis and a configuration of openings separating portions of the stent material, wherein the method further comprises:

providing an elongated element along the axis of the stent structure, wherein the stent structure and the conductive elongated element are spaced a distance apart; and

using the elongated element to provide a gas stream within the defined interior volume of the stent structure.

53. The method of claim 26, wherein providing the medical device comprises providing a cylindrical stent structure defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent an interior volume and at least an exterior surface that is not adjacent to the interior volume, wherein moving a plurality of coating particles towards the at least one surface of the medical device to form a coating thereon is performed with the stent structure in a vertical position such that the stent does not sag along its stent axis.

54. A method of coating a stent structure, the method comprising:

providing a stent structure in a defined volume along a stent axis, wherein the stent structure comprises at least an interior surface adjacent a defined interior volume and at least an exterior surface;

coating at least a portion of the interior surface of the stent structure adjacent the defined interior volume using at least a plurality of first coating particles; and

coating at least a portion of the exterior surface of the stent structure using at least a plurality of second coating particles, wherein the plurality of first coating particles is different than the plurality of second coating particles.

55. The method of claim 54, wherein coating at least a portion of the interior surface of the stent structure adjacent the defined interior volume using at least a plurality of first coating particles comprises:

providing one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end, wherein at least one nozzle structure has at least one opening at the dispensing end thereof located within the defined interior volume of the stent structure;

providing a plurality of first coating particles in the interior defined volume, wherein providing the plurality of first coating particles comprises dispensing a plurality of microdroplets having an electrical charge associated therewith from the dispensing end of the at least one nozzle structure by creating a nonuniform electrical field between the dispensing end and the stent structure, wherein each of the microdroplets comprises at least a particle, and further wherein the electrical charge is concentrated on the particle as the microdroplet evaporates; and

moving the plurality of first coating particles towards the interior surface to form a coating thereon using the nonuniform electrical field created between the dispensing end and the stent structure.

56. The method of claim 55, wherein the at least one nozzle structure comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

57. The method of claim 54, wherein coating at least a portion of the exterior surface of the stent structure using at least a plurality of second coating particles comprises:

providing one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end;

providing a plurality of second coating particles in the defined volume, wherein providing the plurality of second coating particles comprises dispensing a plurality of microdroplets having an electrical charge associated therewith from the dispensing ends of the one or more nozzle structures by creating a nonuniform electrical field between the dispensing ends and the stent structure, wherein each of the microdroplets comprises at least a particle, and further wherein the electrical charge is concentrated on the particle as the microdroplet evaporates; and

moving the plurality of second coating particles towards the medical device to form a coating on the at least one surface of the medical device using the nonuniform electrical field created between the dispensing ends from which the plurality of coating particles is established and the medical device.

58. The method of claim 54, wherein the particles of at least one of the plurality of first coating particles and the plurality of second coating particles have a nominal diameter of less than 10 micrometers and a geometrical standard deviation of less than 1.2.

59. The method of claim 54, wherein the method further comprises controlling an amount of at least one of the plurality of first coating particles and the plurality of second coating particles provided into the interior volume or the defined volume.

60. The method of claim 54, wherein the plurality of first coating particles comprise anti-coagulant particles.

61. The method of claim 54, wherein the plurality of second coating particles comprise anti-inflammatory particles.

62. A system for use in coating at least one surface of a medical device, the system comprising:

a particle source;

a holding fixture operable to position a medical device in a defined volume;

a dispensing device configured to receive source material from the particle source and dispense a plurality of monodisperse coating particles into the defined volume, wherein the dispensing device comprises one or more nozzle structures, wherein each nozzle structure comprises at least one opening terminating at a dispensing end thereof from which a plurality of monodisperse coating particles having an electrical charge applied thereto is dispensed; and

an electrode structure comprising an electrode isolated from the dispensing ends of the one or more nozzle structures, wherein the electrode structure is operable to create a nonuniform electrical field between the dispensing ends of the one or more nozzle structures and the medical device for use in providing the plurality of monodisperse coating particles in the defined volume, wherein the plurality of monodisperse coating particles have a nominal diameter of less than 10 micrometers and a geometrical standard deviation of less than 1.2, and further wherein the nonuniform electric field is operable to assist in moving a plurality of the coating particles towards the at least one surface of the medical device to form a coating thereon.

63. The system of claim 62, wherein the electrode is a grounded medical device.

64. The system of claim 62, wherein the electrode is a ring electrode positioned forward of one or more of the nozzle structures.

65. The system of claim 62, wherein the dispensing device is configured to dispense a spray of microdroplets having an electrical charge associated therewith, wherein each of the microdroplets comprises at least a particle, wherein the electrical charge is concentrated on the particle as the microdroplet evaporates, and further wherein the electrical charge of the microdroplet concentrated on the particle is greater than about 30 percent of the Rayleigh charge limit for the microdroplet.

66. The system of claim 62, wherein the dispensing device is configured to dispense a spray of microdroplets having an electrical charge associated therewith, wherein each of the microdroplets comprises at least a particle, wherein the electrical charge is concentrated on the particle as the microdroplet evaporates, and further wherein the position of the dispensing ends relative to the medical device are such that, prior to contact with the at least one surface of the medical device, a residual particle volume occupied by the evaporated microdroplet comprises less than about 20 percent of a solvent component of the microdroplet.

67. The system of claim 62, wherein the medical device comprises a structure defining an interior volume, wherein the structure comprises at least an interior surface adjacent the interior volume and at least an exterior surface, wherein the holding fixture is operable to position a medical device such that at least one nozzle structure of the dispensing device is operable within the interior volume defined by the structure.

68. The system of claim 67, wherein the electrode structure is operable to create a nonuniform electrical field between the dispensing end of the at least one nozzle structure and the medical device for use in providing the plurality of monodisperse coating particles in the interior volume of the medical device.

69. The system of claim 67, wherein the at least one nozzle structure comprises an elongated element sized to be positioned or moved into the defined interior volume of the medical device.

70. The system of claim 62, wherein the dispensing device comprises a plurality of nozzle structures.

71. The system of claim 62, wherein the holding fixture is configured to hold the medical device in a fixed position within the defined volume.

72. The system of claim 62, wherein the holding fixture is configured for movement of the medical device within the defined volume.

73. The system of claim 62, wherein the holding fixture is configured to receive a stent structure, wherein the stent structure is defined along a stent axis, wherein the stent structure comprises at least an interior surface adjacent a defined interior volume and at least an exterior surface.

74. The system of claim 73, wherein the holding fixture is configured to at least rotate the stent structure about the stent axis.

75. The system of claim 73, wherein the holding fixture is configured to at least move the stent structure linearly along the stent axis.

76. The system of claim 62, wherein the system further comprises a control system operable to control the amount of monodisperse coating particles provided into the defined volume.

77. The system of claim 62, wherein the system further comprises a control system operable to adjust the strength of the nonuniform electrical field.

78. The system of claim 62, wherein the particle source comprises source material for use in providing a plurality of coating particles comprising at least one biologically active ingredient or at least one coated biologically active ingredient.

79. A system for use in coating at least one surface of a medical device, the system comprising:

particle generation apparatus operable to provide a plurality of coating particles in a defined volume;

a holding fixture operable to position a stent structure defined along a stent axis in the defined volume, wherein the stent structure comprises at least an interior surface adjacent an interior volume and an exterior surface, wherein the holding fixture comprises an elongated element located within the interior volume of the stent structure; and

a temperature control apparatus operable to hold the elongated element at a lower temperature than the temperature in the defined volume adjacent the exterior surface of the stent structure such that thermophoretic effect moves the coating particles towards the at least one surface of the stent structure.

80. A system for use in coating at least one surface of a stent structure, the system comprising:

a particle source;

a holding fixture operable to position a stent structure defined along a stent axis in a defined volume, wherein the stent structure comprises at least an interior surface adjacent a defined interior volume and at least an exterior surface;

a dispensing device configured to receive source material from the particle source and dispense a plurality of microdroplets having an electrical charge associated therewith from the dispensing ends of the one or more nozzle structures into the defined volume, wherein each of the microdroplets comprises at least a particle, and further wherein the electrical charge is concentrated on the particles as the microdroplets evaporate resulting in a plurality of coating particles; and

an electrode structure comprising an electrode isolated from the dispensing ends of the one or more nozzle structures, wherein the electrode structure is operable to create a nonuniform electrical field between the dispensing ends of the one or more nozzle structures and the stent structure for use in providing the plurality of coating particles in the defined volume and moving the plurality of coating particles towards the stent structure to form a coating on the at least one surface thereof.

81. The system of claim 80, wherein the electrode is a grounded stent structure.

82. The system of claim 80, wherein the electrode is a ring electrode positioned forward of one or more of the nozzle structures.

83. The system of claim 80, wherein the plurality of coating particles in the defined volume have a nominal diameter of less than 10 micrometers and a geometrical standard deviation of less than 1.2.

84. The system of claim 80, wherein the plurality of microdroplets comprise a plurality of microdroplets that each have electrical charge associated therewith that is greater than about 30 percent of the Rayleigh charge limit for the microdroplet.

85. The system of claim 80, wherein the position of the dispensing ends relative to the stent structure is such that, prior to contact with the at least one surface of the stent structure, a residual particle volume occupied by the evaporated microdroplet comprises less than about 20 percent of a solvent component of the microdroplet.

86. The system of claim 80, wherein the holding fixture comprises:

an elongated substantially non-conductive tube for receiving the stent structure thereon;

an elongated conductive element, wherein at least a portion of the elongated conductive element extends through the elongated substantially non-conductive tube, and further wherein the elongated conductive element comprises a conductive contact section;

a compression apparatus configured to provide for expansion of the elongated substantially non-conductive tube such that an exterior surface thereof is in contact with at least a portion of the interior surface of the stent structure and such that a portion of the stent structure is in electrical contact with the conductive contact section.

87. The system of claim 86, wherein the holding fixture is configured to at least rotate the stent structure about the stent axis.

88. The system of claim 86, wherein the holding fixture is configured to at least move the stent structure linearly along the stent axis.

89. The system of claim 80, wherein the holding fixture is configured to allow at least one nozzle structure of the dispensing device to be operable within the interior volume defined by the stent structure.

90. The system of claim 89, wherein the electrode structure is operable to create a nonuniform electrical field between the dispensing end of the at least one nozzle structure and the stent structure for use in providing the plurality of coating particles in the interior volume of the stent structure.

91. The system of claim 89, wherein the at least one nozzle structure comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

92. The system of claim 80, wherein the holding fixture is configured to hold the stent structure in a fixed position within the defined volume.

93. The system of claim 80, wherein the holding fixture is configured for movement of the stent structure within the defined volume.

94. The system of claim 93, wherein the holding fixture is configured to at least rotate the stent structure about the stent axis.

95. The system of claim 93, wherein the holding fixture is configured to at least move the stent structure linearly along the stent axis.

96. The system of claim 80, wherein the dispensing device comprises a plurality of nozzle structures.

97. The system of claim 96, wherein the dispensing device comprises an elongated cylindrical body member defining an interior volume thereof along an axis, wherein the holding fixture is operable to position the stent structure along the axis of the elongated cylindrical body member, and further wherein the one or more nozzle structures are positioned radially about the axis of the elongated cylindrical body member and linearly along the elongated cylindrical body member in the direction of the axis thereof.

98. The system of claim 97, wherein each of a plurality of the nozzle structures comprises a capillary tube comprised of a body portion and a tapered capillary tip at the dispensing end of the capillary tube.

99. The system of claim 97, wherein each of a plurality of the nozzle structures comprises a tapered portion used to define an opening, and further wherein at least a part of each of the plurality of the nozzle structures extend from an integral conductive portion associated with the body member.

100. The system of claim 97, wherein each of a plurality of the nozzle structures comprises a solid post along a center axis extending through an opening at the dispensing end.

101. The system of claim 97, wherein each of a plurality of the nozzle structures comprises an elongated radial opening in the body member.

102. The system of claim 97, wherein each of a plurality of the nozzle structures comprises an elongated opening in the body member lying parallel to the axis thereof.

103. The system of claim 80, wherein the holding fixture comprises:

an elongated element extending along an axis, the axis of the stent structure coinciding with the axis of the elongated element when received thereon; and

spacing elements operable to maintain a distance between the stent structure and the elongated element.

104. The system of claim 80, wherein the holding fixture comprises an elongated element, wherein the elongated element is sized based on the defined interior volume of the stent structure such that a surface of the elongated element is in direct contact with the interior surface of the stent structure.

105. The system of claim 80, wherein the holding fixture comprises:

a conductive elongated element along the axis of the stent structure, wherein the stent structure and the conductive elongated element are spaced a distance apart; and

a power source configured to create an electric field between the conductive elongated element and the stent structure that is opposite the nonuniform electric field created between the dispensing ends of the nozzle structures and the stent structure.

106. The system of claim 80, wherein the holding fixture comprises an elongated element along the axis of the stent structure, wherein the stent structure and the elongated element are spaced a distance apart, the elongated element configured to provide a gas stream within the defined interior volume of the stent structure.